Lecuture 26 ( Flashcards
How cells become more specialised and less flexible during deveopment - TALKING FROM LECTURE
ALL TALKING FROM SLIDES FOR UNERSTANDING
- during 8 cell stage all are identical
- during cell polarisation - there is a small gap in the middle and around the outside, microvilli are forming - cells are starting to change shape and grab ahold of each other much more tightly by cellecation molecules
- during compaction - cellication cell pulls cells together very tight - embryo goes from right to smooth on the outside microvilli
- during ‘inner’ apolar cells being cut off - there is a second round of cell division - asymmetric cell division - all nuclear DNA is copied and inherited by both daughters -outside and inside cell - outside cells are exposed to interuterine environment - the environment gives cells differences and sends them on completely different paths
- cells in centre go on to develop into embryo - inner cell mass,
- after a few more cell divisions on outside you get a blastocyst,
- cells on outside become trophectoderm - goes on to from some of the placenta
An enbryo begins as…
A small number of naive totipotent cells
Totipotent
Can divide into any of the 200 cell types
Embyionic stem cells can _________________exept__________ which makes them __________
- embryonic stem cells can give rise to all cell types except trophectoderm making them pluripotent
Cells become more specialised and less flexible during development
True and real
A cells fate is ________ until it becomes _______ ________ and can only give rise to __________
A cells fate is progressively limited until it becomes terminally differentiated and can only give rise to same cell type
All cells become more specialised and less flexible during development except….
- stem cells
- germ cells (egg and sperm)
How muscle genes turn into muscle genes from embryo cells LECTURE TALKING
- embryonic cell can become anything it wants - looking at DNA you find different genes - master regulartory gene myoD - when this is activated the cell will become a muscle cell - inside nucleus there are many other genes. ATM the cell isn’t contracting and doesn’t do what a muscle cell does and insnt doing anything that makes it a potential muscle cell as all genes are in the off position - so not producing proteins, but is copied every time the dna divides
- first the cell ends up in a Somite and turns on a gene called myoD - thus startes making mRNA copies and that gets turned into a MyoD protein (transcription factors - go on and turn other genes on
How muscle genes turn into muscle genes from embryo cells
Finally the cell is terminally differentiated, playing a functional role in the organism
- through different environments and experiences specific genes turn on causing a cascade of other genes getting turned on, pushing cells towards a differentiated fate
Genomic equivalence
- differentiated cells contain all the DNA requires to build an entire new organism
- when cells divide they loose no genetic info - have a complete copy of our DNA
- the DNA in a cell nucleaus is the same as all other DNA in other cells nucleaus
- the nuclei in an undifferentiated cell has the same genetic info as one that is differentialted / specialised
Whatever are Embryonic stem cells harvested from?
The inner cell mass (future embryo) of mammalian blastocyst embryos
Human embryonic stem cells are….
Pluripotent - they can develop into any of the 200 cell types of cell in our bodies, given the right conditions
The cells derived from the embryonic stem cells are…
Genetically identical to the embryo donor
How are induced pluripotent stem cells made?
By reprogramming adult skin (undoing all the knots in the DNA that makes it differentiated and turning back on all the embryo genes that make it behave like an embryo) - usually made from fibroblasts or blood
- iPS cells can be made from anyone, and are genetically identical the the source skin cells.
- they are also pluripotent, the can generate any cell type
- don’t have to destroy an embryo
Adult stem cells - how to they differ from embryonic stem cells?
- renew tissues
- stem calls can divide without limit
- they are undifferentiated, multipotent cells (can make 2 or 3 cell types associated with the tissue they live in)
- they can divide to give rise to stem cells and cells which will go on to differentiate into one of more (but not all) types of functional tissue cells
Adult stem cells; renewal tissues
- stem cell divides into another stem cell and a progenitor cell
- progenitor cell goes onto divide to give one of many cell types
